1. Field of the Invention
The present invention relates to an LED lamp with a light guide. More particularly, it relates to an LED lamp with a light guide for use in vehicle, traffic and other automotive/transportation type lamps in general, such as rear combination lamps, rear fog lamps, reverse lamps, turn signal lamps, stop lamps, traffic signal lamps, and tail lamps. The LED lamp may also be used in playing machines, utility lamps, or amusement lamps in general, such as pinball machines, video games, dance lights, festival lights, flash lights, spot lights, game machines, etc.
2. Description of Related Art
FIG. 6 shows a structure of an LED light emitting unit 61 and an optical system in a lamp 60 according to the related art. The lamp can include an LED 51 light source, regarded as a point source of light, and a light guide 54 having a light incident surface, a light exit surface, a primary reflective surface 52, and a secondary reflective surface 53 formed thereon. A light emitted from the light source enters the light guide 54 through the light incident surface formed on the light guide 54. The light is then guided through the light guide 54 toward the primary reflective surface 52. The light reflected at the primary reflective surface 52 is guided through the light guide 54 toward the secondary reflective surface 53. The light reflected at the secondary reflective surface 53 is guided through the light guide 54 toward the light exit surface and finally exits externally through the light exit surface, thus tracing an optical path.
The LED light emitting unit 61 in the lamp 60 is structured such that the light guide 54 is symmetrically formed about a point and the single LED 51 light source is located at the center thereof. The light emitted from the LED 51 and which enters the light guide 54 through the light incident surface is reflected at the primary reflective surface 52 radially toward the rim and guided through the light guide 54. Then, it is reflected at the secondary reflective surface 53, which is formed on a concentric circle centered on the optical axis X of the LED 51 light source, and emitted externally through the light exit surface. Therefore, the light released externally through the light exit surface of the light guide 54 has a substantially equal amount of light per unit area. Accordingly, the lamp has less variation in brightness and better visibility (see JP-A 2002-216510, for example).
The lamp with the LED light emitting unit described above disperses the light emitted from the single LED light source. Therefore, the amount of light per unit area released externally through the light exit surface of the light guide is small and accordingly the lamp has relatively low brightness. The single light source can not release lights of two or more types which limits the applicable range of the lamp.